Experimental and numerical investigation on overbreak control considering the influence of initial support in tunnels. (September 2021)

• Record Type: Journal Article
• Authors: Chen, Jihui; Qiu, Wenge; Zhao, Xuwei; Rai, Partab; Ai, Xufeng; Wang, Hailiang
• Is Part Of: Tunnelling and underground space technology. Volume 115(2021)
• Publication Date: 2021-09
• Subjects: Overbreak -- Underbreak -- Initial support -- Contour blastholes -- Damage -- Drilling pattern; Tunneling -- Periodicals; Underground construction -- Periodicals; Tunnels -- Periodicals; Underground areas -- Periodicals; 624.193
• DOI: 10.1016/j.tust.2021.104017
• Languages: English
• ISSNs: 0886-7798

Abstract

Highlights: Studying the influences of initial support on overbreak and underbreak. Application of LSACB pattern in controlling overbreak and underbreak of tunnel. Invesgating the rock damage mechanism in the LSACB pattern. Giving some suggestions to control overbreak and underbreak. Abstract: The problems of overbreak and underbreak exist widely in drilling and blasting (D&B) tunnels. The pattern of traditional contour blastholes (TCB) has drawbacks in controlling overbreak and underbreak due to neglecting the impacts of the initial support. Generally, it brings about the large look-out angle causing overbreak in engineering. Therefore, this paper put forward the long and short associate contour blastholes (LSACB) pattern which had been applied in metro tunnels in Qingdao, China. Field tests showed that the LSACB pattern can control overbreak better than the TCB pattern. After that, damage models were built to analyze the proposed pattern. For example, the rock damage evolution in the LSACB pattern was discussed. The effects of the unsupported length, initial support thickness, and the advance per round on this pattern were also studied further. Finally, combining the LSACB pattern and the existing technology, some suggestions were put forward to control the overbreak. This paper provided an excellent reference for similar projects.